524
FXUS02 KWBC 120802
PMDEPD
EXTENDED FORECAST DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
302 AM EST WED NOV 12 2025
VALID 12Z SAT NOV 15 2025 - 12Z WED NOV 19 2025
...HEAVY RAIN LIKELY IN SOUTHERN CALIFORNIA SATURDAY, CAUSING
POSSIBLE FLOODING CONCERNS...
..OVERVIEW
A SOUTHERN STREAM UPPER LOW WILL MOVE INTO SOUTHERN CALIFORNIA AND
VICINITY OVER THE WEEKEND, BRINGING WIDESPREAD RAIN THAT MAY CAUSE
FLOODING ON SATURDAY. PRECIPITATION INCLUDING HIGHER ELEVATION
SNOW IS FORECAST TO SPREAD ACROSS MUCH OF THE INTERMOUNTAIN WEST ON
SUNDAY. UPPER RIDGING AHEAD OF THIS SYSTEM WILL LEAD TO MUCH
WARMER THAN AVERAGE TEMPERATURES ACROSS THE CENTRAL TO EASTERN U.S.
OVER THE WEEKEND. MEANWHILE IN THE NORTHERN STREAM, AN UPPER
TROUGH WILL PUSH A SURFACE LOW/FRONTAL SYSTEM ACROSS THE GREAT
LAKES AND NORTHEAST OVER THE WEEKEND, LEADING TO RAIN AND SOME
WINTRY PRECIPITATION. INTO THE WORKWEEK, RAIN IS FORECAST TO SPREAD
INTO THE CENTRAL AND EAST-CENTRAL U.S. AS THE INITIAL UPPER LOW
AND SURFACE FRONTAL SYSTEM LIFTS AND THEN STALLS. YET ANOTHER
TROUGH MAY MOVE INTO THE WEST EARLY NEXT WEEK AND BRING ADDITIONAL
PRECIPITATION CHANCES ACROSS THE REGION.
..GUIDANCE/PREDICTABILITY ASSESSMENT
THE FIRST SYNOPTIC FEATURE OF NOTE IS A SOUTHERN STREAM CLOSED
UPPER LOW THAT RECENT MODELS NOW SHOW OFFSHORE AT THE START OF THE
PERIOD SATURDAY, A SLOWER TREND. THIS LOW SHOULD TRACK EAST INTO
SUNDAY, AND THE ECMWF RUNS SEEM TO SHOW THE MOST CONSISTENT MIDDLE
GROUND SOLUTION COMPARED TO A SLIGHTLY FASTER UKMET, FARTHER SOUTH
CMC, AND FARTHER NORTH GFS RUNS. INTO THE WORKWEEK THERE IS SOME
SPREAD IN THE TRACK OF THE FEATURE AS IT MOVES ACROSS THE CENTRAL
U.S. ALONG WITH A SURFACE LOW. GFS RUNS (ESPECIALLY THE 12Z AND
18Z) WERE NOT FAVORED WITH ITS LOW TRACK, MOVING INTO THE LOWER
OHIO VALLEY EARLY TUESDAY WHILE THE CONSENSUS OF THE REST OF THE
GUIDANCE WAS BACK IN THE MID-MISSISSIPPI VALLEY. HOWEVER, THE NEWER
00Z ECMWF SEEMS TO BE A NORTHERN OUTLIER WITH THE SURFACE LOW.
IN THE BROAD SENSE, UPPER TROUGHING MOVING THROUGH THE NORTH-
CENTRAL TO NORTHEASTERN U.S. THIS WEEKEND INTO EARLY NEXT WEEK
SHOWS MODEL AGREEMENT, AND THE NEW 00Z MODEL RUNS ARE AGREEABLE
WITH THE SURFACE LOW TOO. RIDGING TO ITS SOUTH CAUSING WARM
TEMPERATURES ALSO HAS GOOD CONSENSUS.
FARTHER WEST THOUGH, MODEL SPREAD INCREASES SIGNIFICANTLY AS
TROUGHING MOVES FROM THE EASTERN PACIFIC AND REACHES THE WEST, WITH
UNCERTAINTY REGARDING IF ENERGY WILL PULL SOUTH AND DEVELOP
ANOTHER SOUTHERN STREAM CLOSED LOW EARLY NEXT WEEK OR STAY PHASED.
INTERESTINGLY THE 12/18Z GFS LOOKED SIMILAR TO THE EC-AIFS WITH
FAVORING CLOSED LOW DEVELOPMENT, WHILE THE 12Z ECMWF WAS SIMILAR TO
THE AI-GFS WITH A QUICKER PHASED TROUGH, AS ONE SIGN OF THE
NOTABLE MODEL SPREAD SPREAD. IN TERMS OF THE 00Z MODELS, THE GFS
WAS A BIT ODD WITH DIGGING ENERGY SOUTHWARD FARTHER WEST IN THE
PACIFIC UNLIKE ANY OTHER MODEL. CMC RUNS MAY BE THE BEST MIDDLE
GROUND, SHOWING UPPER LOW DEVELOPMENT BUT NOT COMPLETE SEPARATION
OF THE STREAMS. NO NOTABLE MODEL PREFERENCE AT THIS POINT FOR
SEPARATED OR PHASED TROUGHING AS WE AWAIT BETTER MODEL CONVERGENCE.
THE WPC FORECAST WAS BASED ON A BLEND FAVORING THE 12Z ECMWF WITH
LESSER PROPORTIONS OF THE 18Z GFS AND 12Z CMC EARLY ON, INTRODUCING
AND GRADUALLY INCREASING THE PROPORTION OF ENSEMBLE MEANS IN THE
BLEND AS THE PERIOD PROGRESSED AND MODEL SPREAD INCREASED.
..WEATHER/HAZARDS HIGHLIGHTS
THE SOUTHERN STREAM CUTOFF LOW MOVING INTO SOUTHERN CALIFORNIA
WILL PROVIDE DYNAMICAL SUPPORT FOR AMPLE PRECIPITATION, MOSTLY
RAIN, ACROSS SOUTHERN CALIFORNIA AND INTO THE SOUTHWEST ON
SATURDAY. PRECIPITABLE WATER VALUES WILL LIKELY BE OVER THE 95TH
PERCENTILE FOR THIS TIME OF YEAR, AND SOME MODEST INSTABILITY
EXISTS AHEAD OF AND UNDERNEATH THE DEEP UPPER LOW. A SLIGHT RISK OF
EXCESSIVE RAINFALL HAS BEEN INTRODUCED FOR MUCH OF SOUTHERN
CALIFORNIA IN SATURDAY'S ERO WITH THIS SLOW-MOVING SETUP CAUSING
SCATTERED FLOODING CONCERNS, ESPECIALLY FOR SENSITIVE AREAS LIKE
BURN SCARS AND URBAN AREAS. 2 TO 5 YEAR ARI EXCEEDANCES MAY BECOME
COMMON IN DESERT AREAS THAT DO NOT OFTEN SEE THIS MUCH RAIN. BY
SUNDAY THE UPPER LOW LOOKS TO LIFT NORTHEAST AND LOSE THE DEEPER
MOISTURE CONNECTION, BUT WIDESPREAD LIGHT TO MODERATE PRECIPITATION
IS LIKELY ACROSS THE INTERMOUNTAIN WEST. PRECIPITATION SHOULD BE
MOSTLY RAIN EVEN INTO PARTS OF THE MOGOLLON RIM, BUT FARTHER NORTH
INTO THE HIGHER ELEVATIONS OF THE CENTRAL ROCKIES SNOW IS LIKELY.
WILL HOLD OFF ON ANY EXCESSIVE RAINFALL AREAS ON DAY 5/SUNDAY DUE
TO THE LESSENING MOISTURE LEVELS AND THE UNCERTAINTY IN PLACEMENT.
RAIN AND POSSIBLY THUNDERSTORMS MAY SPREAD EAST LATER SUNDAY AND
ESPECIALLY INTO MONDAY ACROSS THE PLAINS AND MISSISSIPPI VALLEY,
AND PERHAPS STALLING IN THE SOUTH-CENTRAL U.S. STRETCHING INTO THE
OHIO/TENNESSEE VALLEYS ON TUESDAY BUT WITH GREATER UNCERTAINTY.
BROAD PRECIPITATION CHANCES ARE LIKELY ACROSS THE NORTHEASTERN
QUADRANT OF THE CONUS OVER THE WEEKEND AS A LOW PRESSURE SYSTEM
MOVES THROUGH. ACCUMULATING SNOW IS LIKELY IN THE INTERIOR
NORTHEAST, ESPECIALLY IN HIGHER ELEVATIONS, AND SOME FAVORED AREAS
COULD SEE FREEZING RAIN.
PERIODIC PRECIPITATION IS LIKELY ACROSS THE PACIFIC NORTHWEST AND
INTERMOUNTAIN WEST INTO THE WEEKEND, WITH HIGHER ELEVATION SNOW. BY
SUNDAY, PRECIPITATION CHANCES SHOULD RAMP UP INTO NORTHERN
CALIFORNIA AND FARTHER INLAND AS WELL, AS BROAD UPPER TROUGHING
APPROACHES. TROUGHING LOOKS TO MOVE THROUGH THE WEST EARLY NEXT
WEEK AND COULD SPREAD PRECIPITATION ACROSS THE INTERMOUNTAIN WEST
ONCE AGAIN, THOUGH THE DETAILS REMAIN UNCERTAIN. PRECIPITATION
COULD BE MODERATE OR HEAVY AT TIMES.
TEMPERATURES ARE FORECAST TO BE WARMER THAN AVERAGE FOR MUCH OF
THE CENTRAL AND EAST-CENTRAL U.S. ON SATURDAY. 80S WILL BE
WIDESPREAD ACROSS TEXAS, AND HIGHS REACHING THE UPPER 70S WELL INTO
THE MID-MISSISSIPPI VALLEY AND OHIO VALLEY WILL BE 15 TO 25
DEGREES ABOVE NORMAL. TEMPERATURES IN THE NORTHERN TIER SHOULD COOL
IN THE NORTHERN U.S. SUNDAY AND MONDAY, BUT THE SOUTH-CENTRAL TO
SOUTHEAST U.S. LOOKS TO STAY ABOVE AVERAGE. MEANWHILE THE ROUNDS OF
TROUGHING IN CALIFORNIA TO THE SOUTHWEST WILL LEAD TO BELOW
AVERAGE HIGHS THERE MOST DAYS.
TATE
ADDITIONAL 3-7 DAY HAZARD INFORMATION CAN BE FOUND ON THE WPC
MEDIUM RANGE HAZARDS OUTLOOK CHART AT:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/THREATS/THREATS.PHP
WPC MEDIUM RANGE 500MB HEIGHTS, SURFACE SYSTEMS, WEATHER GRIDS,
QUANTITATIVE PRECIPITATION FORECAST (QPF), EXCESSIVE RAINFALL
OUTLOOK (ERO), WINTER WEATHER OUTLOOK (WWO) PROBABILITIES, HEAT
INDICES, AND KEY MESSAGES CAN BE ACCESSED FROM:
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST500_WBG.GIF
HTTPS://WWW.WPC.NCEP.NOAA.GOV/MEDR/5DAYFCST_WBG_CONUS.GIF
HTTPS://WWW.WPC.NCEP.NOAA.GOV/5KM_GRIDS/5KM_GRIDSBODY.HTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/QPF/DAY4-7.SHTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=ERO
HTTPS://WWW.WPC.NCEP.NOAA.GOV/WWD/PWPF_D47/PWPF_MEDR.PHP?DAY=4
HTTPS://WWW.WPC.NCEP.NOAA.GOV/HEAT_INDEX.SHTML
HTTPS://WWW.WPC.NCEP.NOAA.GOV/#PAGE=OVW
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